Crime Busters
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Transcript of Crime Busters
Crime Busters
Piedmont IB SOWorkshop #2
What is required for success
• Chemistry knowledge• Common sense• Logical thinking• memory• Speed !• Work hard!
What you will learn
• Chemistry• Flow charts/problem solving skills
Topics covered
• Powders• Metals (nationals)• Liquids (nationals)• Fibers and plastics• Paper chromatography• Crime Scene Physical Evidence• Evidence analysis
Powders
Able to identify the following powders• Sodium acetate• Sand• Calcium carbonate (powdered
limestone)• Vitamin C (Ascorbic acid)• Table salt• Sugar• Flour
• Cornstarch• Baking soda• Powdered gelatin• Powdered Alka-Seltzer• Yeast• Borax• talc
Metals(Nationals only)
• Aluminum• Iron• Zinc• Magnesium• Copper• tin
Liquids(Nationals only)
Able to identify the following liquids• Lemon juice• Rubbing alcohol• Household ammonia• Water• Vinegar• Hydrogen peroxide
Polymers, hair and fibers
Hair (National)• Human• Dog• Cat
Polymers• PETE• HDPE• Non-expanded
PS• LDPE• PP• PVC
Fibers (national)• Animal• vegetable• synthetic
Paper chromatograph(National)
• To identify ink, juices, and other colored materials
• Easy to do. Compare unknown with known materials
Physical evidence
• Finger prints– Patterns (whorls, loops, arches)– Compare known to unknown
• Irises
Evidence analysis
• Logical thinking• Speed and clarity
How to identify powders• Appearance/physical
properties– Color– Texture– Odor/smell– Density
• Water solubility/pH• Reaction with HCl
– Rate of reaction– Gas formation– Disappearance of insolubles– smell
• Reaction with Iodine• Other characteristics
Example of powder identification
Sodium acetate• Colorless needles or white
powder• Very water soluble• pH = 8.9• Smells like vinegar when
HCl is added, no other visible reactions
pH of aqueous solution Crystal form Powder form Water solubility 1 M HCl Iodine reagent Other CharacteristicsAnhydrous sodium acetate 8.9 very soluble vinegar smell
How to identify Metals• Appearance/physical properties
– Color– Is it shiny?– Density– Attraction by magnet
• Reaction with HCl– Rate of reaction– Gas formation– Heat generation
How to identify liquids
• Smell• Clarity• pH
How to identify hair
• Microscope• Visual observation
How to identify fibers- only required to distinguish between animal, natural, and synthetic
• Physical properties– Diameter of fiber– Is it straight or curled?– Is it stretchy?– Micrographs provided
• Burning observations (provided)
How to identify plastics
• Appearance– Color– Clarity– Density, using solutions of known density
• Burning properties
Paper chromatography
• Separation of colors (possibly)
• Relative position of spots
• Used to identify the source of ink, juice, and other colored materials
Finger prints
• Remember the different patterns– Whorls– Loops– Arches
• Compare unknown with knowns– Could be partial prints– Know where to look at
DNA
• Similar to paper chromatography in principle, but uses high tech to look at DNA patterns
• Compare known with unknown• Use common sense
Shoeprints and tire treads
• Patterns• Speed and direction of travel
Irises
• Unique like finger print• Some EU countries started using Iris scan